<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            background-color: #999;
        }

        .box {
            width: 300px;
            height: 300px;
            border: 3px solid pink;
        }
    </style>
</head>

<body>
    <!--  HTML内联框架元素 (<iframe>) 表示嵌套的browsing context。它能够将另一个HTML页面嵌入到当前页面中。-->
    <div class="box">
        <iframe src="http://www.baidu.com" style="width: 100%;height:100%;" frameborder="0"></iframe>
    </div>
</body>

</html>